1. Field of the Invention
This invention relates to a vehicle safety device suitably used for, for example, electric vehicles.
2. Description of the Related Art
FIG. 4 is a diagram of the configuration of a conventional vehicle safety device used, for example, in a power circuit of an electric propulsion system for an electric vehicle.
Referring to FIG. 1, a battery 1 is provided as a power source for driving the electric vehicle. The positive terminal of the battery 1 is connected to a controller 3 through a fuse 2 for preventing a short-circuit accident, while the negative terminal of the battery 1 is connected directly to the controller 3. The controller 3 supplies driving current to an alternating current motor 4 for the controlled driving thereof. The alternating current motor 4 is connected to a drive mechanism (not shown) for driving the vehicle.
The operation of this system will be described below.
A current supplied from the battery 1 flows through the fuse 2 into the controller 3. The current is controlled by the controller 3 and then flows into the alternating current motor 4 to generate a driving force in the alternating current motor 4. The vehicle drive mechanism is driven by the driving force of the alternating current motor 4.
When a short-circuit occurs in the power circuit, the fuse 2 is melted and cut by a large current to break the current path between the battery 1 and the controller 3 to maintain safety.
In the conventional vehicle safety device thus constructed, the power circuit is not cut off even when a vehicle collision occurs, unless a short-circuit occurs in the electric circuit. Upon such a collision, if a failure occurs in the controller 3 or an accelerator device (not shown) or if a driver in an unconscious state depresses the accelerator pedal, an electric current is supplied to the alternating current motor 4. There is therefore a risk of the vehicle running away.